58Nevertheless, it must be borne in mind that the amount referred to in point 25 of the Guidelines is part of the basic amount of the fine which, as is apparent from point 19 of the Guidelines (see paragraph 21 above), must reflect the gravity of the infringement and not the relative gravity of the participation in the infringement of each of the undertakings concerned. According to the case-law, the latter issue has to be examined in the context of the possible application of aggravating or mitigating circumstances (see, to that effect, Case T-73/04Carbone-Lorraine v Commission [2008] ECR II-2661, paragraph 100). Accordingly, and as the Commission correctly states, the Commission may determine the percentage of the value of sales referred to in point 25 of the Guidelines, as well as that referred to in point 21 of the Guidelines, at the same level for all cartel participants. The determination of the same percentage for all cartel participants does not, contrary to what the applicant appears to be claiming, mean that the same sum has been determined under point 25 of the Guidelines for all the cartel participants. In so far as that sum is a percentage of the value of each cartel participant’s sales in relation to the infringement, it will be different for each participant, depending on the differences in the value of participants’ sales.